Thermal stability of Si/Si1−x−yGexCy/Si quantum wells grown by rapid thermal chemical vapor deposition

The thermal stability of Si/Si1−x−yGexCy/Si quantum wells was studied by high resolution x-ray diffraction, Fourier transform infrared spectroscopy, and defect etching. There are different pathways of strain relaxation in this material system, depending on the annealing temperature. The lattice structure of Si1−x−yGexCy was as stable as the Si1−xGex alloys at an annealing temperature of 800 °C for 2 h. At an annealing temperature of 900 °C for 2 h, the structures of both Si1−x−yGexCy and Si1−xGex started to relax. The addition of C enhanced the Ge outdiffusion in Si1−x−yGexCy, compared to that of Si1−xGex. For the annealing temperatures of 950 and 1000 °C for 2 h, the Si1−xGex continued to relax with the decrease of strain in the quantum wells, but the Si1−x−yGexCy relaxed with the increase of the strain due to the formation of SiC precipitates. Misfit dislocation formation was observed in the Si1−x−yGexCy alloys with initial thicknesses below the critical thickness after annealing at 1000 °C for 2 h. This relaxation is probably caused by the SiC precipitation, since SiC precipitates can reduce the strain compensation and, therefore, decrease the critical thickness.